Process for antimicrobial treatment of fresh produce, particularly mushrooms

ABSTRACT

Preservative compositions using toxicologically acceptable ingredients, and employing a pH of 9.0 or above for at least part of the process, for reducing the initial population and controlling the growth of spoilage bacteria and human pathogens and for preventing unwanted color changes in fresh and processed produce, particularly mushrooms. Aqueous solutions of preservatives are prepared and applied in multiple stages to the mushrooms, by spraying or immersion. More specifically, disclosed is a method for preserving fresh and processed mushrooms, comprising the steps of: contacting the mushrooms with an antimicrobial solution having a pH of about 9.0 or above; and rinsing the mushrooms one or more times immediately after the contacting step with pH-neutralizing solutions having a pH sufficient to return the produce to its physiological pH. In a preferred embodiment, electrolyzed basic water is used in the first stage high-pH rinse step and electrolyzed acid water is used in the second stage neutralizing solution step. Tyrosinase inhibitors such as ascorbates, erythorbates, EDTA or calcium chloride are added to the neutralizing solutions to inhibit enzymatic browning.

FIELD OF THE INVENTION

[0001] The present invention relates generally to processes for reducingbacterial population and retarding spoilage and other unwanted qualitychanges in fresh and processed produce, particularly mushrooms, that areintended for ingestion by humans and lower animals, and morespecifically to antimicrobial aqueous washes, especially those employinga pH of about 9.0 or above as part of the process, which are especiallysuitable for practicing said processes.

BACKGROUND OF THE INVENTION

[0002] Consumers identify whiteness and cleanliness of fresh mushroomsas the principal factors determining the quality thereof. Consumersprefer to purchase mushrooms that are bright white and free of casingmaterial, compost, or other unwanted particulate contaminants clingingto the surfaces thereof.

[0003] Commercial mushroom cultivation practices, typically growingmushrooms in straw-bedded horse manure compost covered with a fine layerof peat or other “casing material,” yields mushrooms with unwantedparticulate contaminants clinging to the mushroom cap and othersurfaces, giving an undesirable appearance. Moreover, mushrooms aretypically harvested by hand, introducing a potential source ofcontamination by human pathogens in addition to the normally presentfluorescent pseudomonads and other spoilage organisms that lead toaccelerated tissue decay and discoloration.

[0004] Mushroom discoloration (browning and purple blotch) occurs when apolyphenol oxidase enzyme (tyrosinase), which naturally occurs at highlevels in mushroom cap cuticle (surface) tissue, interacts with phenolicsubstrates, also naturally occurring in mushroom tissue, to produce thebrown pigment melanin. In healthy, intact mushroom tissue, the enzymeand its substrates are located in separate subcellular compartments, andare therefore prevented from reacting to form colored pigments.Unfortunately, mushroom tissue deteriorates with time due to severanceand is highly susceptible to damage by bacterial action or by physicalhandling, and this damage allows the browning enzyme and its substratesto interact, resulting in unwanted color changes in the mushroom tissue.

[0005] It would be highly desirable, therefore, to provide a commercialpreservative treatment in the form of efficacious processing aids toprevent bacterial damage to mushroom tissue, indirectly preventingdiscoloration, and to inhibit directly the polyphenol oxidase-mediatedbrowning reaction. Moreover, it would be especially desirable tointroduce process aids in the form of a spray or wash that would removecompost, casing material, and other unwanted particulate materialclinging to mushroom surfaces.

[0006] Prior to 1986, aqueous solutions of sulfite, particularly sodiummetabisulfite, were used to wash mushrooms for the purpose of removingunwanted particulate matter, and to enhance mushroom whiteness. In 1986,however, the U.S. FDA banned the application of sulfite compounds tofresh mushrooms, due to severe allergic reactions to sulfites amongcertain asthmatics.

[0007] Following the ban on sulfite compounds for processing of freshmushrooms, there have been several efforts to develop wash solutions foruse as a suitable replacement for sulfites. While sulfite treatmentyields mushrooms of excellent initial whiteness and overall quality, itdoes not inhibit the growth of spoilage bacteria. Therefore, the qualityimprovement brought about by sulfite use is transitory. After 3 days ofrefrigerated storage, bacterial decay of sulfited mushrooms becomesevident. Traditionally, this was not a concern to mushroom growers,because sulfite washes were inexpensive, effective at removing unwantedparticulates, and gave excellent initial quality.

[0008] The banning of sulfite washes, however, gave researchersincentive not only to find a suitable sulfite replacement, but also toimprove upon sulfite washes by developing a preservative treatment whichwould extend washed mushroom shelf life beyond that attainable bysulfiting, and which would improve storage quality over that of sulfitedmushrooms. McConnell developed an aqueous preservative wash solutioncontaining 10,000 parts per million (ppm) hydrogen peroxide and 1000 ppmcalcium disodium EDTA. The hydrogen peroxide serves as an antimicrobialagent, while EDTA enhances antimicrobial activity and directlyinterferes with the enzymatic browning reactions. Copper is a functionalcofactor of the mushroom browning enzyme, tyrosinase, and tyrosinaseactivity is dependent upon copper availability. EDTA binds copper morereadily than does tyrosinase, thereby sequestering copper and reducingtyrosinase activity and associated discoloration of mushroom tissue.

[0009] Hydrogen peroxide acts as a bactericide by causing oxidativedamage to DNA and other cellular constituents. Sapers adaptedMcConnell's hydrogen peroxide treatment, incorporating hydrogen peroxideinto a two-stage mushroom wash, employing 10,000 ppm hydrogen peroxidein the first stage and 2.25% or 4.5% sodium erythorbate, 0.2%cysteine-HCL, and 500 ppm or 1000 ppm EDTA in aqueous solution in thesecond stage. Hydrogen peroxide treatments typically yielded mushroomsnearly as white as sulfited mushrooms initially, and whiteness surpassedthat of sulfited mushrooms after 1-2 days of storage at 12° C., andshelf life was dramatically improved. Hydrogen peroxide, however, is notcurrently approved for treatment of fresh produce. More efficacy andsafety data are required. Moreover, as the browning reaction itself isoxidative, it would be advantageous to employ a non-oxidative agent,rather than a strong oxidizer such as hydrogen peroxide, for controllingbacterial growth.

[0010] U.S. Pat. No. 5,919,507 to Beelman et al., which is herebyincorporated by reference in its entirety for all purposes, generallydiscloses a process of treating mushrooms with a first stage high-pHaqueous solution and then rinsing the mushrooms with a second stageneutralizing wash or washes. The neutralizing wash preferably contains abuffered solution of erythorbic acid and sodium erythorbate.

SUMMARY OF THE INVENTION

[0011] The present invention provides a sulfite alternative employinghigh pH wash (preferably a pH of about 9.0 or above) to controlbacterial growth on mushrooms followed by an antimicrobial neutralizingwash or washes preferably containing browning inhibitors to minimizeenzymatic browning of mushroom tissue. In one embodiment, theantimicrobial neutralizing wash is followed by a separate antioxidantwash containing the browning inhibitors. In a preferred embodiment,electrolyzed basic water is used in the high-pH wash and electrolyzedacidic water is used in the neutralizing wash.

[0012] High pH (9.0 or above) has been shown to be effective forcontrolling the growth of bacteria in egg washwater. The presentinvention uses high-pH solutions as an antimicrobial wash treatment forfresh produce, particularly mushrooms, to prevent bacterial decay ofproduce tissue and resultant tissue browning. With their highsusceptibility to tissue damage, mushrooms represent a uniqueapplication of high-pH preservative treatments. Solution exposure timemust be carefully controlled, to optimize bacterial destruction whileavoiding counterproductive overexposure of mushrooms to extremes of pH,resulting in chemical damage to tissue. Thus, the present inventioncomprises a multiple-stage wash procedure, with an initial high-pHantimicrobial step, followed by a second antimicrobial neutralizing steputilizing one or more pH neutralization and/or browning inhibitorwashes.

[0013] The present invention provides a high-pH treatment for thecontrol of bacterial spoilage of mushrooms. A first-stage, high-pH washdestroys bacteria, but might also directly damage mushroom tissue. Thisis avoided, however, if mushroom exposure time to the high-pH solutionis brief and is followed in rapid succession by a second-stageneutralizing buffer solution.

[0014] A principal objective of the present invention is to provide apractical wash treatment that will yield mushrooms as white assulfite-treated mushrooms initially, while reducing bacterialpopulations and also suppressing bacterial growth, extending shelf life,and improving storage quality.

[0015] It is a principal object of the present invention to apply highpH bactericidal solutions to mushrooms followed by neutralization ofmushroom pH and introduction of browning inhibitors, to preventbacterial decay and mushroom tissue discoloration.

[0016] Further, it is an object of this invention to accomplish theabove-noted objectives in as cost efficient manner as possible usingcompositions and wash solutions having regulatory approval to be used asprocess aids for treatment of fresh produce.

[0017] In general, the foregoing objectives are accomplished byproviding a process for a high pH wash treatment wherein the mushroomsare contacted first with a highly basic aqueous solution followed byrinsing with a neutralizing solution wash or washes. In a preferredembodiment the first stage basic solution comprises electrolyzed basicwater and the second stage antimicrobial neutralizing solution compriseselectrolyzed acidic water. In another preferred embodiment, the secondstage neutralizing solution comprises fumaric acid and sodium benzoate.Optionally, a third stage antioxidant neutralizing solution wash may beadvantageously employed comprising browning inhibitors such asascorbate, erythorbate, EDTA and/or calcium chloride, particularly whenthe second stage neutralizing solution does not contain or containsminimal browning inhibitors.

[0018] Preservative compositions using toxicologically acceptableingredients, and employing a pH of 9.0 or above for at least part of theprocess, for reducing the initial population and controlling the growthof spoilage bacteria and human pathogens and for preventing unwantedcolor changes in fresh and processed produce, particularly mushrooms.Aqueous solutions of preservatives are prepared and applied in multiplestages to the mushrooms, by spraying or immersion. More specifically,disclosed is a method for preserving fresh and processed mushrooms,comprising the steps of: contacting the mushrooms with an antimicrobialsolution having a pH of about 9.0 or above; and rinsing the mushroomsone or more times immediately after the contacting step withpH-neutralizing solutions having a pH sufficient to return the produceto its physiological pH. In a preferred embodiment, electrolyzed basicwater is used in the first stage high-pH rinse step and electrolyzedacid water is used in the second stage neutralizing solution step.Tyronase inhibitors such as ascorbates, erythorbates, EDTA or calciumchloride are added to the neutralizing solutions to inhibit enzymaticbrowning.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The wash treatments of the present invention consist of twostages: a first-stage, high-pH antimicrobial wash (a pH of 9.0-11.8),followed by a second-stage neutralization wash or washes. Typically, theantimicrobial wash comprises a basic sodium or potassium carbonate orbicarbonate aqueous solution. The first stage wash is followed in rapidsuccession by a neutralizing wash or washes to return the surface pH ofthe mushrooms to the physiological pH of mushrooms. Preferably, theneutralization wash comprises browning inhibitors such as ascorbate,erythorbate, calcium chloride, and EDTA.

[0020] Any suitable high-pH aqueous solution having sufficientlybactericide effect may be used as the first stage high-pH wash. Examplesof two chemically modified solutions prepared at pH 11.0, a suggested pHfor useful antimicrobial action, are as follows: a 0.05M sodiumbicarbonate solution (pH 8.25) adjusted to pH 11.0 with 1.0N sodiumhydroxide, and a 1% tribasic sodium phosphate solution (pH 11.74)adjusted to pH 11.0 with 42.5% phosphoric acid. Sodium or potassiumcarbonate or bicarbonate buffer solutions having a pH in the range ofabout 9 to 11.8 are preferred.

[0021] It has also been found that basic solutions of electrolyzed watermay be advantageously used in the first stage high-pH wash. Electrolyzedwater is typically produced using pure water with no added chemicalsexcept sodium chloride (NaCl). Commercial electrolyzed water generatorsare available, for example, from Amano Corporation of Yokohama, Japan,Aiken Industrial Co., Ltd. of Japan or Hoshizaki Electric Co. Ltd. ofAichi, Japan. The generation of electrolyzed water involves reactions ina cell containing inert positively-charged and negatively-chargedelectrodes separated by a membrane through which a very dilute saltwater solution passes. Two types of water are generated: electrolyzedbasic water (aqueous solutions having a pH of about 11.4 and a lowoxidation-reduction potential (ORP), i.e., a reducing potential thatleads to the reduction of free radicals in biological systems, typicallylower than −700 mV) and electrolyzed acidic water (aqueous solutionshaving a pH 2.2 to 3.0 and a high ORP, typically greater than +1100 mV,with residual free chlorine of 10 to 80 ppm).

[0022] Electrolyzed basic water may be used as the first stage high-pHsolution either alone or chemically modified. The electrolyzed basicwater may be buffered with, for example, a suitable acid such ashydrochloric, citric or fumaric acid.

[0023] Since high pH is employed as the principal antimicrobial factor,it is necessary to neutralize pH in the second wash stage, to minimizeproduce tissue damage and resultant acceleration of enzymatic browning.

[0024] As previously taught in U.S. Pat. No. 5,919,507, the neutralizingsolutions used in the neutralizing wash may comprise a variety ofaqueous solutions including a simple water wash. The important factor isthat the pH on the surface of the produce or mushrooms be returned toits physiological pH (in the case of mushrooms, about 6.5) as rapidly aspossible in order to minimize enzymatic browning.

[0025] Neutralizing solutions may include food grade acidulants such aserythorbic acid, ascorbic acid, fumaric acid, and citric acid, as wellas acetic acid, phosphoric acid, malic acid, lactic acid, gluconic acid,hydrochloric acid, sulfuric acid or the like and combinations thereof.Preferably, the acidulants are present in a buffered solution. From acommercial standpoint, citric acid, fumaric acid, benzoic acid andcombinations thereof are particularly useful acidulants due to therelative lower cost, ease of handling, and enzymatic browning inhibitingproperties and approval for use on edible products. In general, theacidulant will maintain the neutralizing solution pH in the range of 2to 5.5, preferably a pH of 3 to 5 and will comprise between 0.1 to 3percent by weight, preferably 0.5 to 1.0 percent by weight of theneutralizing solution. The neutralizing solutions are preferablyformulated in accordance with the present invention to impartantimicrobial activity as well as pH-neutralizing properties.

[0026] The wash solutions may also comprise ozonated water having anozone concentration of 1-20 ppm, preferably 5 ppm or greater. Theozonated water wash may be employed in conjunction with an initial highpH wash or separately without such high pH wash. Preferably the ozonatedwater wash is followed by an antioxidant wash using a solutioncontaining browning inhibitors. Alternatively, browning inhibitors maybe incorporated in the ozonated water solution in, for example, theconcentrations noted elsewhere herein.

[0027] Preferably, the neutralizing solution also comprises browninginhibitors to further inhibit enzymatic browning. Any suitable knownbrowning inhibitor may be used such as ascorbates and erythorbates,preferably in the range of 1 to 4 percent by weight of the neutralizingsolution. Other known browning inhibitors include EDTA, calcium chlorideand the like. The preferred range of EDTA is 0.01 to 0.3 percent byweight and the preferred range of calcium chloride is 0.01 to 2, morepreferably 0.05 to 0.15, percent by weight of the neutralizing solution.

[0028] It has been found that a pH-neutralizing solution comprisingfumaric acid and sodium benzoate (or associated acid) has particularlyeffective antimicrobial properties when used in the present invention.Preferably, the fumaric acid/benzoate combination is present in therange of 0.1 to 3 percent by weight of the solution.

[0029] Preferably, where chlorine is present, the available chlorineconcentration in the pH-neutralizing solution is in the range of 5-200ppm Cl₂ and/or 1-50 ppm ClO₂. The addition of stabilized chlorinedioxide in Stage 1I or Stage III neutralizing washes beneficiallyinhibits the build up of bacteria on the produce that may otherwiseoccur, thereby providing a longer shelf life for the produce. Theantimicrobial properties of the wash are enhanced when stabilizedchlorine dioxide is employed in a neutralizing wash having an acidic pHand/or in a neutralizing wash at neutral pH where free chlorine is alsopresent. It has also been found that the addition of benzoic acid in theStage II or Stage III neutralizing washes also advantageously inhibitsbacteria build up on the produce.

[0030] Electrolyzed acidic water may be used as the neutralizingsolution in the second stage. Preferably, browning inhibitors such asascorbates, erythorbates, EDTA and calcium chloride are added to thesolution. In a preferred embodiment, electrolyzed acidic water isbuffered with an erythorbate salt such as sodium erythorbate, preferablyin the range of 0.2 to 4 percent by weight of the neutralizing solution.Optionally, acidulants such as those noted above may also be used incombination with electrolyzed acidic water.

[0031] The use of electrolyzed basic water and electrolyzed acidic waterin the present invention provides several advantages. Electrolyzed watercan be produced on site relatively inexpensively using commerciallyavailable generators. The production of electrolyzed water is relativelysimple and does not require extensive handling and maintaining ofchemicals such as concentrated acids. Further, when both the basic andacidic solutions are used in the process, the residual washes can bedisposed of in an environmentally sound manner, i.e., the electrolyzedbasic water and electrolyzed acidic water can be combined to produce aneutral aqueous solution that can be discharged without any harm to theenvironment or special wastewater processing.

[0032] The two stage treatment process described herein may be appliedto mushrooms or other produce by either dipping or spraying the requiredsolutions and thus the process is feasible for continuous operation. Thesecond stage neutralizing wash may be accomplished in a single wash ormultiple washes.

[0033] Optionally, a third stage pH-neutralizing/browning inhibitor washmay be used. In this embodiment, the solutions of the third stage washcomprise browning inhibitors such as ascorbate, erythorbate, EDTA andcalcium chloride. The use of a third stage wash is particularlyadvantageous where the second stage neutralizing solution does notcomprise any browning inhibitors or comprises only minimal anti-browningagents. When browning inhibitors are present in the second stagesolution, the third stage wash may serve to enhance the anti-browningeffect of the overall wash process.

[0034] The following examples are included herein to illustratepreferred embodiments of this invention.

EXAMPLE 1

[0035] A first stage solution is prepared using deionized water, 0.42percent weight sodium bicarbonate and sodium hydroxide to adjust thesolution pH to 10.5 at 25° C. A neutralization stage aqueous solution isprepared containing 0.15 weight percent fumaric acid and 0.15 weightpercent sodium benzoate having a pH of 3.5. The neutralization stagesolution is chilled to 10° C. Mushrooms are washed in 3.5-literpolyethylene buckets, at a ratio of 300 g of mushrooms per liter of washsolution. The mushrooms are washed for 30-60 seconds in the first stagesolution and then immediately transferred to the second stageneutralization solution and immersed for an additional 30 seconds, for atotal wash time of 90 seconds. In both wash stages, mushrooms are gentlyagitated by hand.

EXAMPLES 2-6

[0036] The same procedure as set forth in Example 1 is followed, usingthe following formulations for first and second stage solutions. Allsolutions are described as weight percent of each component except whereindicated. Exam- Stage I Stage II ple High-pH Sol'n Neutralizing Sol'n 2Sodium bicarbonate 0.42% Sodium Erythorbate 2.0% Sodium hydroxide toadjust Citric Acid 0.4% pH to 10.5 EDTA 0.1% Calcium Chloride 0.1% pH =4.3 3 Sodium bicarbonate 0.42% Sodium Erythorbate 2.0% Sodium hydroxideto adjust Fumaric Acid 0.3% pH to 10.5 EDTA 0.1% Calcium Chloride 0.1%pH = 4.2 4 Electrolyzed basic water Electrolyzed acidic water (pH 2.3,(pH 11.4, ORP −795 mV) ORP +1150) Adjusted to pH 10.5 with SodiumErythorbate 2.0% fumaric acid pH = 4.5 5 Electrolyzed basic water SodiumErythorbate 2.0% (pH 11.4, ORP −795 mV) Fumaric Acid 0.3% Adjusted to pH10.5 with EDTA 0.1% fumaric acid Calcium Chloride 0.1% pH = 4.2 6 Sodiumbicarbonate 0.42% Electrolyzed acidic water (pH 2.3, Sodium hydroxide toadjust ORP +1150) pH to 10.5 Sodium Erythorbate 2.0% pH = 4.5 7 Sodiumbicarbonate 0.42% Sodium Erythorbate, 1.6% Sodium hydroxide to adjustErythorbic Acid 0.4% pH to 10.5 Chlorine dioxide 5 ppm pH 5.0

EXAMPLES 8-14

[0037] The procedure as set forth in Example 1 is employed with therinse times as indicated, using the following formulations for first andsecond stage solutions. Additionally, the mushrooms are washed in athird stage neutralizing solution containing browning control agentsfollowed by a water spray rinse. All solutions are described as weightpercent of each component except where indicated. Stage I High-pH StageIV Antimicrobial Stage II Stage III Water Rinse Sol'n Low-pHAntimicrobial Low-pH Neutralizing & 5-15 sec. 15-45 sec. & NeutralizingSol'n Browning Control Sol'n (spray Example (60-100° F.) 15-45 sec.(50-90° F.) 15-45 sec. (40-80° F.) @40-70° F.)  8 Sodium Fumaric acid,0.3% Sodium Erythorbate, Water bicarbonate 0.42% Sodium benzoate, 0.3%1.6% Sodium hydroxide pH 3.5 Erythorbic Acid 0.4% to adjust pH to EDTA,0.1% 10.5 Calcium Chloride, 0.1% pH 5.0  9 Electrolyzed basicElectrolyzed acidic Sodium Erythorbate, Water water (pH 11.4, water (pH2.7, 2.4% ORP −795 mV) ORP +1150 mV) Erythorbic acid, 0.6% EDTA, 0.1%Calcium Chloride, 0.1% pH 5.2 10 Electrolyzed basic Fumaric acid, 0.3%Sodium Erythorbate, Water water (pH 11.4, Sodium benzoate, 1.0-3.0% ORP−795 mV) 0.15% EDTA, 0.1% pH 3.5 Calcium Chloride, 0.1% pH 4.8 11 SodiumCitric acid, 0.3-1.0% Sodium Erythorbate, Water bicarbonate 0.42% Adjustto pH 5.5 with 1-3% Sodium hydroxide NaOH Erythorbic acid, to adjust pHto +50 ppm Cl₂ 0.2-0.6% 10.5 +5 ppm ClO₂ EDTA, 0.1% (stabilized) CalciumChloride, 0.1% pH 5.2 12 Sodium Ozonated water Sodium Erythorbate, Waterbicarbonate 0.42% (ORP +1,256 mV) 1-3% Sodium hydroxide Citric acidbuffered to Erythorbic acid, to adjust pH to pH 4.5 0.2-0.6% 10.5 EDTA,0.1% Calcium Chloride, 0.1% pH 5.2 13 — Ozonated water SodiumErythorbate, Water (ORP +1,256 mV) 1-3% Erythorbic acid, 0.2-0.6% EDTA,0.1% Calcium Chloride, 0.1% pH 5.2 14 Sodium Fumaric acid, 0.3% SodiumErythorbate, Water bicarbonate 0.42% Sodium benzoate, 1-3% Sodiumhydroxide 0.15% Erythorbic acid, to adjust pH to pH 3.5 0.2-0.6% 10.5Chlorine dioxide 5 ppm (stabilized) pH 5.2

[0038] The process of the present invention is particularly useful inthe antimicrobial treatment of mushrooms. It can also be advantageouslyemployed in connection with other produce products such as fresh fruitsand vegetables and, in particular, produce susceptible to enzymaticbrowning.

What is claimed is:
 1. A process for preserving fresh and processedmushrooms, comprising the steps of: (a) contacting the mushrooms with afirst antimicrobial solution comprising electrolyzed basic water havinga pH of at least about 9.0; (b) rinsing the mushrooms after saidantimicrobial contacting step with a pH-neutralizing solution having apH sufficient to return the mushrooms to the mushroom physiological pHof about 6.5.
 2. The process of claim 1, wherein the neutralizingsolution comprises an acidulant selected from the group consisting ofascorbic acid, erythorbic acid, citric acid, fumaric acid andcombinations thereof.
 3. The process of claim 3, wherein theneutralizing solution comprises the acidulant in the range of 0.1 to 3percent by weight and the pH of the neutralizing solution is in therange of 2 to 5.5.
 4. The process of claim 2, wherein the neutralizingsolution comprises a browning inhibitor.
 5. The process of claim 4,wherein the browning inhibitor is selected from the group consisting ofascorbate, erythorbate, EDTA and calcium chloride.
 6. The process ofclaim 4, wherein the neutralizing solution comprises the browninginhibitor in the range of 1 to 4 percent by weight and the browninginhibitor is selected from the group consisting of ascorbate,erythorbate and a combination thereof.
 7. The process of claim 1,wherein the neutralizing solution comprises electrolyzed acidic water.8. The process of claim 2, wherein the acidulant is fumaric acid and theneutralizing solution further comprises sodium benzoate or benzoic acid.9. The process of claim 1, said process further comprising the step of:(c) rinsing the mushrooms with a second pH-neutralizing solutioncomprising a browning inhibitor.
 10. The process of claim 9, wherein thebrowning inhibitor is selected from the group consisting of ascorbate,erythorbate, EDTA and calcium chloride.
 11. A process for preserving afresh produce product, comprising the steps of: (a) contacting the freshproduce product with a first antimicrobial solution comprisingelectrolyzed basic water having a pH of at least about 9.0; (b) rinsingthe fresh produce products after said antimicrobial contacting step witha pH-neutralizing solution having a pH sufficient to return the surfacepH of the fresh produce product to the physiological pH of the freshproduce product.
 12. The process of claim 11, wherein the neutralizingsolution comprises electrolyzed acidic water.
 13. The process of claim12, wherein the neutralizing solution comprises a browning inhibitor.14. The process of claim 13, wherein the browning inhibitor is selectedfrom the group consisting of ascorbate, erythorbate, EDTA and calciumchloride.
 15. The process of claim 13, wherein the neutralizing solutioncomprises the browning inhibitor in the range of 1 to 4 percent byweight and the browning inhibitor is selected from the group consistingof ascorbate, erythorbate and a combination thereof.
 16. The process ofclaim 11, wherein the neutralizing solution comprises an acidulantselected from the group consisting of ascorbic acid, erythorbic acid,citric acid, fumaric acid and combinations thereof.
 17. The process ofclaim 16, wherein the neutralizing solution comprises the acidulant inthe range of 0.1 to 3 percent by weight and the pH of the neutralizingsolution is in the range of 2 to 5.5.
 18. The process of claim 16,wherein the neutralizing solution comprises a browning inhibitor. 19.The process of claim 18, wherein the browning inhibitor is selected fromthe group consisting of ascorbate, erythorbate, EDTA and calciumchloride.
 20. The process of claim 18, wherein the neutralizing solutioncomprises the browning inhibitor in the range of 1 to 4 percent byweight and the browning inhibitor is selected from the group consistingof ascorbate, erythorbate and a combination thereof.
 21. The process ofclaim 11, wherein the neutralizing solution further comprises fumaricacid and sodium benzoate.
 22. The process of claim 11, said processfurther comprising the step of: (c) rinsing the fresh produce productwith a second pH-neutralizing solution comprising a browning inhibitor.23. The process of claim 22, wherein the browning inhibitor is selectedfrom the group consisting of ascorbate, erythorbate, EDTA and calciumchloride.
 24. A process for preserving a fresh produce product,comprising the steps of: (a) contacting the fresh produce product with afirst antimicrobial solution having a pH of at least about 9.0; (b)rinsing the fresh produce products after said antimicrobial contactingstep with a pH-neutralizing solution comprising electrolyzed acidicwater having a pH sufficient to return the surface pH of the freshproduce product to the physiological pH of the fresh produce product.25. The process of claim 24, wherein the neutralizing solution comprisesa browning inhibitor.
 26. The process of claim 25, wherein the browninginhibitor is selected from the group consisting of ascorbate,erythorbate, EDTA and calcium chloride.
 27. The process of claim 25,wherein the neutralizing solution comprises the browning inhibitor inthe range of 1 to 4 percent by weight and the browning inhibitor isselected from the group consisting of ascorbate, erythorbate and acombination thereof.
 28. The process of claim 24, said process furthercomprising the step of: (c) rinsing the mushrooms with a secondpH-neutralizing solution comprising a browning inhibitor.
 29. Theprocess of claim 28, wherein the browning inhibitor is selected from thegroup consisting of ascorbate, erythorbate, EDTA and calcium chloride.30. A process for preserving fresh and processed mushrooms, comprisingthe steps of: (a) contacting the mushrooms with a first antimicrobialsolution having a pH of at least about 9.0; (b) rinsing the mushroomsafter said antimicrobial contacting step with a pH-neutralizing solutionhaving a pH sufficient to return the mushrooms to the mushroomphysiological pH of about 6.5 comprising an acidulant selected from thegroup consisting of citric acid, fumaric acid, benzoic acid andcombinations thereof.
 31. The process of claim 30, wherein theneutralizing solution comprises a browning inhibitor.
 32. The process ofclaim 31, wherein the browning inhibitor is selected from the groupconsisting of ascorbate, erythorbate, EDTA and calcium chloride.
 33. Theprocess of claim 31, wherein the neutralizing solution comprises thebrowning inhibitor in the range of 1 to 4 percent by weight and thebrowning inhibitor is selected from the group consisting of ascorbate,erythorbate and a combination thereof.
 34. The process of claim 30,wherein the neutralizing solution comprises electrolyzed acidic water.35. The process of claim 30, said process further comprising the stepof: (c) rinsing the mushrooms with a second pH-neutralizing solutioncomprising a browning inhibitor.
 36. The process of claim 35, whereinthe browning inhibitor is selected from the group consisting ofascorbate, erythorbate, EDTA and calcium chloride.
 37. The process ofclaim 30, wherein the first pH-neutralizing solution comprises 1 to 50ppm chlorine dioxide.
 38. The process of claim 35, wherein the firstpH-neutralizing solution comprises 1 to 50 ppm chlorine dioxide.
 39. Aprocess for preserving fresh and processed mushrooms, comprising thesteps of: (a) contacting the mushrooms with a first antimicrobialsolution having a pH of at least about 9.0; (b) rinsing the mushroomsafter said antimicrobial contacting step with a pH-neutralizing solutionhaving a pH sufficient to return the mushrooms to the mushroomphysiological pH of about 6.5 comprising fumaric acid and sodiumbenzoate; and (c) rinsing the mushrooms with a second pH neutralizingsolution comprising a browning inhibitor.
 40. The process of claim 39,wherein the browning inhibitor is selected from the group consisting ofascorbate, erythorbate, EDTA and calcium chloride.
 41. The process ofclaim 39, wherein the neutralizing solution of step (c) comprises thebrowning inhibitor in the range of 1 to 4 percent by weight and thebrowning inhibitor is selected from the group consisting of ascorbate,erythorbate and a combination thereof.
 42. A process for preservingfresh and processed mushrooms, comprising the steps of: (a) contactingthe mushrooms with a first antimicrobial solution having a pH of atleast about 9.0; (b) rinsing the mushrooms after said antimicrobialcontacting step with a pH-neutralizing solution comprising ozonatedwater.
 43. The process of claim 42, further comprising the step of: (c)rinsing the mushrooms with a second pH neutralizing solution comprisinga browning inhibitor.
 44. The process of claim 43, wherein the browninginhibitor is selected from the group consisting of ascorbate,erythorbate, EDTA and calcium chloride.
 45. The process of claim 44,wherein the neutralizing solution of step (c) comprises the browninginhibitor in the range of 1 to 4 percent by weight and the browninginhibitor is selected from the group consisting of ascorbate,erythorbate and a combination thereof.
 46. A process for preservingfresh and processed mushrooms, comprising the steps of: (a) contactingthe mushrooms with a first antimicrobial solution comprising ozonatedwater; and (b) rinsing the mushrooms with a neutralizing solutioncomprising a browning inhibitor.
 47. The process of claim 46, whereinthe browning inhibitor is selected from the group consisting ofascorbate, erythorbate, EDTA and calcium chloride.
 48. The process ofclaim 47, wherein the neutralizing solution of step (c) comprises thebrowning inhibitor in the range of 1 to 4 percent by weight and thebrowning inhibitor is selected from the group consisting of ascorbate,erythorbate and a combination thereof.
 49. A process for preservingfresh and processed mushrooms, comprising the steps of: (a) contactingthe mushrooms with a first antimicrobial solution having a pH of atleast about 9.0; (b) rinsing the mushrooms after said antimicrobialcontacting step with a pH-neutralizing solution having a pH sufficientto return the mushrooms to the mushroom physiological pH of about 6.5comprising a browning inhibitor and chlorine dioxide.
 50. A process forpreserving fresh and processed mushrooms, comprising the steps of: (a)contacting the mushrooms with a first antimicrobial solution having a pHof at least about 9.0; (b) rinsing the mushrooms after saidantimicrobial contacting step with a pH-neutralizing solution having apH sufficient to return the mushrooms to the mushroom physiological pHof about 6.5; and (c) rinsing the mushrooms with a second pHneutralizing solution comprising a browning inhibitor and chlorinedioxide.